An object of mass 1.15 kg is attached to a horizontal spring and set sliding bac
ID: 1642075 • Letter: A
Question
An object of mass 1.15 kg is attached to a horizontal spring and set sliding back and forth on a frictionless surface, oscillating between the points x1 = -0.158 m and x2 = 0.158 m. While it oscillates, you measure that it takes 129 s for the object to complete 81 full back-and-forth oscillations. What is the kinetic energy of the mass and spring when the mass is at the point x1 = -0.158 m? What is the kinetic energy of the mass and spring when the mass is at the midpoint between x1 = -0.158 m and x2 = 0.158 m?
Explanation / Answer
at extreme point, mass will be at rest.
so KE at x = - 0.158 m , KE = 0 ..........Ans
When at midpoint,
T = 129 / 81 = 1.59 sec ....Time period
w = 2pi / T = 3.94 rad/s
v_max = A w = 0.158 x 3.94 = 0.623 m/s
KE = m v_max^2 / 2
= 1.15 x 0.623^2 /2
= 0.223 J .......Ans
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